Intravital microscopy will be used to obtain morphometric data, pressure, volumetric flow and hematocrit distribution in the microcirculation of skeletal muscle of the rat and cat. The data will be used to calculate segmental resistances as a means of establishing the nature and site of control mechanisms. In addition, the terminal lymphatic system will be mapped out by micro-injection procedures for these muscle preparations. Control data on normotensives will then be compared with rats in various stages of spontaneous hypertensive vascular disease. Linear network analysis will be used to compare transcapillary fluid exchange with lymphatic drainage. BIBLIOGRAPHIC REFERENCES: Schmid-Schoenbein, G.W. and B.W. Zweifach: RBC velocity profiles in arterioles and venules of the rabbit omentum. Microvasc. Res. 10:153-164, l975. Hargens A.R. and B.W. Zweifach: Transport between blood and peripheral lymph in intestine. Microvasc. Res. 11:89-101, l976. $ Res., 1976).